Color electrophotography



May 30, 1961 E. K. KAPRELIAN COLOR ELECTROPHOTOGRAPHY 4 Sheets-Sheet 1 Filed Dec. 6, 1955 IN V EN TOR May 30, 1961 E. K. KAPRELIAN 2,986,466 COLOR ELECTROPHOTOGRAPHY Filed Dec. 6, 1955 5 4 Sheets-Sheet 2 IN V EN TOR May 30, 1961 E. K. KAPRELIAN COLOR ELECTROPHOTOGRAPHY 4 Sheets-Sheet 3 Filed Dec. 6, 1955 INVENTOR COLOR ELECTROPHOTOGRAPHY Filed D80. 6, 1955 4 Sheets-Sheet 4 294 292 290 IN V EN TOR United States Patent COLOR ELECTROPHOTOGRAPHY Edward K. Kaprelian, Weatogue, Conn. (29 Riveredge Road, Red Bank, Calif.)

Filed Dec. 6, 1955, Ser. No. 551,288

7 Claims. (Cl. 96-1) This invention relates to color photography employing the principles of electrophotography whereby photographs are produced through the action of light on an electrostatically charged photoinsulator.

The use of such certain photoinsulators as selenium, anthracene, zinc oxide, etc. to produce photographs is well known in xerography and Electrofax. In the usual method a thin layer of the photoinsulator is given an electrostatic charge and this charged plate or sheet is exposed in a camera or printer. Wherever the light strikes the surface of the plate the charge leaks off in proportion to the amount of light, with the result that a latent image of varying electrostatic potentials is produced on the plate surface. This latent image is next developed by applying to the plate surface a finely divided, usually pigmented, material which by selective attraction to the plate produces a visible powder image. This image can be fixed on the plate or sheet or may in turn, be transferred to another surface and fixed there by various means well known in the art.

One typical method of electrostatic electrophotography utilizes a rotating drum which, as it rotates, receives the following treatment at successive stations:

(1) The photoinsulator surface, usually selenium, receives an electrostatic charge.

(2) The charged surface receives light in the pattern of the desired image, and the charge leaks off selectively to produce an electrostatic image.

(3) The electrostatic latent image is developed into visible form by the application of a suitable finely divided powder.

(4) The powder is transferred to a paper or similar base.

(5) The transferred powder image is fixed through the application of heat or a solvent.

(6) The plate surface is cleaned preparatory to repetition of the cycle.

The system described above is employed in the rapid production of black and white copies of both line and continuous tone originals. With greater electrophotographic plate sensitivities extending through the red end of the spectrum it is possible to achieve practical panchromatic response for printing applications.

It is an object of this invention to produce color reproductions from colored originals utilizing electrophotographic methods.

Another object of this invention is to produce color photographic copies continuously from color originals.

Still another object of this invention is to provide the color masking necessary to obtain correct color rendition.

Still another object of this invention is to produce reproductions rapidly and at low cost.

These and other objects of the invention will become apparent from the specification and drawings in which Fig. 1 shows diagrammatically an electrophotographic color printer employing a plurality of projection heads.

Fig. 2 shows diagrammatically an electrophotographic printer employing a single projection head.

5 ice Fig. 3 shows the front view of a head for producing multiple copies of a single original.

Fig. 4 shows in side elevational cross section the head of Fig. 3 along lines 4-4.

Fig. 5 shows diagrammatically a multiple head printer employing charge transfer means for color masking.

Fig. 6 shows diagrammatically a multiple head printer employing one type of electronic link for achieving color masking.

Fig. 7 shows diagrammatically a multiple head color printer employing another type of electronic link for achieving color masking.

The printer shown in Fig. 1 employs a plurality of printing heads 12, 14 and 16 each of which receives, in succession, frames of a color original in the form of a color transparency on a length of film 18. The heads are of usual construction, each employing a suitable lamp and condenser system. The film is moved by means of a sprocket wheel or suitable roller synchronously with the electrophotographic drums to be described.

Projection lenses 24, 26 and 28 receive light from heads 12, 14 and 16 respectively and project through filters 36, 38 and 40, respectively, past slits 42, 48 and 52 and onto drums 56, 58 and 60 respectively. The iris diaphragms in lenses 24, 26 and 28 are controlled by suitable means such as servo motors 30, 32 and 34 respectively. The slits 42, 48 and 52 are formed by pairs of movable vanes 44 which are adjustable through control means 46, 50 and 54 respectively.

As drum 56 rotates in the direction shown each point of its surface is subjected successively to the action of a charging station 62, an exposure station at slit 42, a developing station 64, a transfer station 66 and a cleaning station 68. Drums 58 and 60 receive similar treatment at similar stations. A web 70 of suitable paper base receives the powder image from drums 56 at transfer station 66 and continues past a fixing station 72 where the first transferred image is fixed to the paper. The paper is carried past transfer station 74 of drum 58 where it receives a second image, fixing station 76 where the second image is fixed, and through transfer station 78 and fixing station 80 of drum 60 where a third image is transferred and fixed.

Each projection head and its associated lens, filter, drum and transfer station provides the paper surface with one of the three colors required in producing a color print. Thus each drum receives an optical color separation image and converts this into electrostatic potentials. The pattern of potentials constitutes an electrostatic latent color image, which when developed with the proper color developer produces a color image corresponding to the original separation image. Color filter 36 and the color of the developer powder in developing station 64 are matched to produce the required results. Corresponding developer powders at drums 58 and 60 are matched especially to the required response to light being passed by filters 38 and 40.

It is important to drive drums 56, 58 and 60 synchronously with each other and with the original transparency strip 18 in order to avoid streaking of the image. This is achieved through suitable gearing or toothed belting and a transmission 82. It is also necessary that the web length between stations 66, 74 and 78 be maintained accurately in order that the three colored images will register properly with each other. The web lengths can be adjusted by providing a slightly ofiset adjustable idler between each transfer station for the purpose of varying the web length. It is possible to achieve print density and color balance control through the independent action of each lens diaphragm and each slit. Initially each slit can be separately adjusted through their respec- 'tive control means 46, and 54 to compensate for drum response to the particular light source and filter employed. The lens diaphragms can then be adjusted to the setting which produces a suitable overall print density. Changes in density from frame to frame of the original material can be compensated for automatically through photoelectric means not shown, which will regulate control means 30, 32 and 34. Changes in color balance from frame to frame of the original material can be compensated for by pre-coding the necessary corrections and operating controls 46, 50 and 54 in response to suitable signals produced by the code.

The arrangement shown in Fig. 1 is suitable for one-to-one reproduction only, but obviously could be modified for utilizing reflection type color photographs as the originals in place of the transparencies shown in the drawings.

The color printer shown in Fig. 2 is capable of producing enlarged prints and utilizes a single head. Projection head illuminates film 92 which is moved in the direction shown through the action of sprocket 94. Sprocket 94 is driven through suitable gearing or toothed belting 96 from a transmission 98. The moving film is imaged by lens 100 onto electrophotographic drums 102, 104 and 106, through filters 108, and 112, respectively, by means of semi-transparent mirrors 114 and 116 and mirror 118, respectively to form thereon electrostatic color separation images of varying potentials. Suitable slits 120 control the width of the exposure area at the drums. The drums are driven synchronously with sprocket 94 through transmission 98 and suitable gearing or toothed belting 122.

Each electrophotographic drum prints one color on the print. While three drums as shown are necessary in order to achieve the minimum acceptable print quality it is obvious that a fourth or black printing drum could be added, if desired, in order to improve rendition in a manner well known in the art.

Drum 102 is successively charged at station 130, exposed at slit 120 and developed by a color developer at developing station 132 to form the first of the three necessary color images. This first color is transferred to paper 134 at transfer station 136 and the transferred first color image is fixed at fixing station 138. The drum continues to rotate, is cleaned at cleaning station 142 and repeats its cycle. The paper passes around a roller on its way to the next transfer station in order to pro vide the path length necessary for registry of the images. The second transfer station 144 adds the second color image on top of and in registry with the first color image, fixing is accomplished at fixing station 146 and the web continues around roller 148 to receive and have fixed the third color at transfer station 150 and fixing station 152 respectively. The printed web is wound on take-up reel 154. In this modification density control can be achieved by adjusting the diaphragm in lens 100 and the color balance by varying the widths of slits 120. The developers used are preferably finely divided colored resins employed either as a powder cloud or as a toner on carrier beads, although colored smoke or atomised ink sprays can be used if desired.

It is sometimes desirable to produce a number of color prints from one single original rather than from a strip. It is possible by utilizing the head shown in Figs. 3 and 4 in place of head 90 in Fig. 2 to achieve this result. The light source comprises a high intensity gas and metal vapor discharge tube having lead wires 162 and mounted on the machine frame 172 so as to be intersected by the optical axis of the projection lens. An optically polished glass tube 164 is mounted at its inner end on a rotating support 166 which is provided with a ring gear 168 and carried by an accurate bearing 170 on the frame 172 of the machine. Gear 168 is engaged by gear 174 which in turn is driven by drive means such as 96 shown in Fig.

2. The transparency 176 to be reproduced is wrapped about a glass cylinder 178 and both are inserted into glass cylinder 164. The action of the glass cylinders and their enclosed transparency, rotated through a synchronous gear train, is interchangeable with that of the normal linear feed head such as 90.

Fig. 5 shows a further modification of the invention whereby color masking can be achieved during printing to provide improved color rendition. In this modification a roll of film is fed past a series of projection stations comprising projection head 192, 194, 196, 198 and 200, and projection lenses 202, 204, 206, 208 and 210 respectively. The feeding is achieved by means of rolls 212 which are synchronized in their movement with the drums 222, 252, 224, 254 and 256 respectively in the manner previously described.

Projection heads 192 and 196, which provide the masking action, utilize masking filters 218 and 220 and prisms 214 and 216 respectively for reversing the image direction. The reversing prisms are necessary because light from these two systems reach electrophotographic drums 222 and 224, which are rotating in the direction opposite to that of the other three drums. Slits 226 control the light reaching the drums. Drums 222 and 224 are provided with the usual charging stations 228 and coact with electrostatic image transfer rollers 230 and 232 respectively which are provided with their own charging stations 234. Transfer rollers 230 and 232 are also provided with means for removing residual electrostatic images such as grounding conductors 236 which may be in the form of a fine tinsel brush or a suitable radioactive source for ionizing the air. While the action of light on drums 222 and 224 produces electrostatic latent images in the usual way these images are not developed on the drum. Instead these images are transferred to transfer rollers 230 and 232, which may or may not be electrostatically charged, in a manner described in my copending application Ser. No. 551,289, filed concurrently with this application. The transfer rollers in turn contact adjacent electrostatic images carrying drums to modify the images thereon, as will be described below.

Projection heads 194, 198 and 200 provide imaging for the three colors and utilize color filters 246, 248 and 250 and prism systems 240, 242 and 244, respectively, the latter increasing the path length in each system to match the path length of the masking projectors. The three images are projected on drums 252, 254 and 256 respectively each of which is provided with the usual charging, developing and cleaning stations, as shown diagrammatically but which do not require further description. The three drums also cooperate with transfer stations 262, 264 and 266 respectively while drums 252 and 254 have, in addition, electrostatic transfer stations 258 and 260, respectively, which cooperate with the transfer rollers previously described. Paper 268 from a suitable roll passes through transfer stations 262, 264 and 266 as well as through 3 fixing stations 270 and is wound on reel 272.

Operation of this printer is as follows. Assume first that masking filter 218 is red, filters 246 and 220 are green, filter 248 is blue and filter 250 is red. It follows then that drum 252 prints the magenta image, drum 254 prints the yellow image and drum 256 prints the cyan image. As a given frame passes head 192 its red separation image to be used for masking is recorded as an electrostatic latent color image of varying potentials which is transferred on to rollers 230. This frame next passes head 194 and an electrostatic image corresponding in potentials to the desired green separation component is recorded on drum 252 as an electrostatic latent color image. The electrostatic image on drums 230 corresponding to the red masking image and the electrostatic image on drum 252 corresponding to the green separation image meet at transfer station 258 and form a composite electrostatic image thereon corresponding to the green ease-see separation image, is modified to thereby prevent unwanted magenta colored developer from printing in cyan areas in much the same way as a green-record separation negative is modified by a positive mask obtained from the red-record separation negative in conventional subtractive color photography masking. In order to obtain the desired results proper polarities must be observed and correct voltage gradients maintained. At transfer station 262 the corrected, masked magenta colored powder image is transferred to paper 262 and fixed at fixing station 270.

The given frame next passes head 196 and an electrostatic image corresponding in potentials to the desired green masking image is recorded on drum 224 and transferred to transfer drum 232. This same frame then passes head 198 and its blue electrostatic image is recorded on drum 254. This electrostatic color separation image is modified by the green masking image to prevent unwanted yellow from printing on magenta areas. At transfer point 264 the masked yellow image is added to the masked magenta image already on paper 262 and is fixed at fixing station 270.

The frame to be printed next passes head 200 and the electrostatic image corresponding to the red separation image is recorded on drum 256. This image, ordinarily requiring no masking, is developed, without masking, as a cyan image and transferred onto the magenta and yellow images already on the paper and fixed at fixing station 270 on its way to take up reel 272. Idler rolls 274 are adjustable and are for the purpose of insuring good registry of the various images. Obviously, the cyan image could also be masked and a black printer could be added, if desired.

The masking printer shown in Fig. 6 employs an electronic link for providing suitable masking. This modification comprises three color stations indicated generally at 290, 292 and 294 which are identical except for the color filters and developer colors employed. Station 290 comprises a printing head 300 and a masking head 302. A frame of film first passes head 300 and its green component is recorded as an electrostatic color separation image on electrophotographic drum 308 through lens 384 and green filter 306. This frame next passes head 302 and its red component is received onto an image pickup tube 314 through lens 310 and red filter 312. The resultant signal passes through amplifier 316 where it is amplified, converted to a negative image and fed to picture tube 318, the image on the face of which is relayed through lens 320 to the surface of drum 308 in synchronism with the electrostatic image corresponding to the green component. The reversal image produced by the image reverser system 314316-318 added by lens 320 on top of the image produced by lens 304 acts to selectively reduce the charge remaining in certain areas of the electrostatic image corresponding to the green component, so that compensation is made for the unwanted part of the spectrum passed by the green filter. The distribution of light in the two images projected on drum 308 is such that the masking accomplished is the full equivalent of that in silver photography. For example lens 304 and filter 306 pass enough energy in the form of light to provide 50% to 70% of the required exposure. The remaining 30% to 50% is provided through tube 318 and lens 320. Amplifier 316 is provided with an inverse characteristic so that its output is at a maximum (cor.- responding to an output on tube 318 equal to V2 the total required exposure) when the light passing through filter is above a given threshold. As the amount of light passing through filter 312 increases (corresponding to a condition calling for more masking) the gain in amplifier 316 is reduced with the result that less light corresponding to the red image is added. This is the equivalent of removing light from the green image as through a red mask.

Station 292 and 294 are the yellow and cyan printers as U respectively and are provided with suitable filters for making the blue and red separations respectively with or without masking as desired.

As a result of this masking treatment drum 3 08 prints a masked magenta image on a web of paper 324 as the latter passes a transfer station 326. The transferred image is fixed and the web continues to transfer station 330 where the masked yellow image is transferred and is fixed at station 332. At station 334 the cyan image, masked if necessary, is printed onto the fixed magenta and yellow images and is itself fixed at station 336.

The printer shown in the modification Fig. 7 utilizes a magenta printer, a yellow printer, and a cyan printer denoted generally at 342, 344 and 346 respectively. An original film 340 passes successively through each printer and the three resulting colored images are printed in registry on a web of paper or other suitable base in a manner similar to that employed in the modification in Figs. 5 and 6.

The operation of the magenta printer is as follows. As a given frame of film 340 passes under light head 348 it is imaged by lens 350 through semi transparent mirror 352, green filter 354 and semi transparent mirror 356 onto magenta printer drum 358. Part of the light at mirror 352 is reflected through red filter 360 onto the face 362 of the electronic image reverser system shown diagrammatically at 364. This tube produces at its face 366 a negative image which, through the action of mirror 368, lens 370, mirror 372 and mirror 356 is in turn imaged on drum 358 in coincidence with the image passing through filter 354. The electrostatic image which results from the action of these two light images becomes the masked image for the magenta printer. The magenta developer is applied to drum 358 at station 374, transferred to web 376 at station 378 and fixed to the base at fixing station 384.

The frame of film passes through yellow and cyan printers 344 and 346 and the corresponding masked yellow and cyan images are transferred to the web at stations 382 and 386 respectively and are fixed at stations 384 and 388 respectively.

I claim:

1. A method of continuously producing a strip of electrophotographic prints in natural color from a continuously moving color original through three-color printing techniques comprising the steps of projecting through a color separation filter a continuously moving first color separation image, independently forming through a masking filter a continuously moving first color masking image, combining on a first continuously moving electrophotographic plate surface sensitive to said first color separation image, said first color separation image and said first color masking image in registry to produce a first electrostatic color masked separation image developing said first electrostatic color masked separation image with a first color developer to produce a color separation image having a color bearing substractive relation to said first color separation filter, transferring said color separation image to a continuously moving color print support material, permanently fixing said transferred first color separation image to said support material, repeating said color separation and color masking steps for a second separation color through separation and masking filters for said second color to produce a second electrostatic color masked color separation image on a second continuously moving charged electrophot0 graphic plate surface sensitive to said second masked color separation image, developing said second electrostatic color masked separation image with a second color developer to produce a second continuously moving 8 color separation image having a color bearing a subtractive relation to said second color separation filter, transferring said second color separation image onto said print support material and in registry with said first color separation image, permanently fixing said transferred second color separation image to said support material, repeating at least said color separation step for a third separation color through a separation filter for said third color to produce a third electrostatic color separation image on a third continuously moving electrophotographic plate surface sensitive to said third masked color separation image, developing said third electrostatic color separation image with a third color developer to produce a third continuously moving color separation image having a color bearing a subtractive relation to said third color separation filter, transferring said third color separation image onto said print support material and in registry with said first and second color separation images and permanently fixing said transferred third color separation image to said support material.

2. A method of color masking in the electrophotographic production of a color print from a color original, comprising the steps of exposing said color original onto an electrophotographic plate through a color separation filter to form thereon an electrostatic color separation image of varying electrostatic potentials, exposing said color original through a masking filter onto a second electrophotographic plate to form thereon an electrostatic masking image of varying electrostatic potentials, physically transferring the charges of said electrostatic masking image from said second electrophotographic plate through the medium of an electrically insulating carrier surface onto said first electrophotographic plate and in superimposed registry with said electrostatic color separation image to form a composite masked electrostatic color separation image, and developing said masked electrostatic color separation image with a developer ma terial to a color bearing a subtractive relation to that of the color separation filter.

3. A method of color masking in the electrophotographic production of a color print from a color original, comprising the steps of exposing said color original through a color separation filter onto an electrophotographic plate to form thereon an electrostatic color separation image of varying electrostatic potentials, forming an image of said color original through a masking filter onto the face of an image pickup tube, amplifying and electrically inverting the resulting output signal from the tube, forming on a picture tube the image from said amplified, inverted signal, imaging said picture tube image onto said electrophotographic plate and in superimposed registry with said electrostatic color separation image to provide a color masking correction thereto, and developing the resulting masked electrostatic color separation image with a developer material to a color bearing a subtractive relation to that of the color separation filter.

' 4. A method of color masking in the electrophotographic production of a color print from a color original, comprising the steps of illuminating said color original, receiving the light from said color original into a projection lens, separating the light leaving the projection lens into two portions, forming with some of the light leaving the projection lens, through a color separation filter, a color separation image of said color original, forming with the remainder of the light leaving the projection lens, through a masking filter, a masking image of said color original, receiving said masking image on the receiving face of an image tube, electronically reversing the tones of said maskingimage within said tube and presenting a negative masking image at the picture face of said tube, receiving said negative masking image into a second projection lens, reimaging said negative masking image onto and in coincidence with said color separation image to form therewith a masked color separation image, receiving said masked color separation image on an electrophotographic plate, and developing the resulting masked electrostatic color separation image With a developer having a color bearing a subtractive relation to that of the color separation filter.

5. An electrophotographicprinter apparatus for continuously producing electrophotographic color prints from original color subjects comprising a plurality of projection heads, means for continuously transporting a strip of color subjects successively through said projection heads, a plurality of electrophotographic printing heads and means for continuously transporting a strip of print receiving material through said printing heads, each of said projection heads comprising a light source, a lens for producing an image of said color original, and light filter means for modifying the color of said image, the filters in said projection heads acting successively as a first color masking filter, a first color separation filter, a. second color masking filter, a second color separation. filter and a third color filter; a first electrop-hotographic drum receiving an image from said first projection head, a second electrophotographic drum receiving an image from said second projection head, electrostatic charge transfer roller means between said first and second electrophotographic drums; a first printing head comprising said second drum, a second drum developing station and a second drum image transfer station; third and fourth electrophotographic drums receiving images from said third and fourth projection heads, electrostatic charge transfer roller means between said third and fourth electrophotographic drums, a second printing head comprising said fourth drum, a fourth drum developing station and a fourth drum image transfer station; a fifth electrophotographic drum receiving an image from said fifth projection head, and a third printing head comprising said fifth drum, a fifth drum developing station and a fifth drum image transfer station.

6. An electrophotographic printer apparatus for continuously producing electrophotographic color prints from original color subjects comprising means for continuously moving a strip of color subjects successively through a plurality of projection stations, said projection stations each comprising a light source for illuminating the color original, a projection lens for producing an image of the. color original and a color filter for modifying the color of the image, the first of said stations being provided with a color separation filter for a first color, a first rotating electrophotographic drum for receiving the image from said first projection station, the second of said projection stations being provided with a masking filter for said first color, an image pickup tube receiving the image produced by said second station, an amplifier for reversing the tones in said second station image, a picture tube for displaying said reversed image, a picture tube projection lens for projecting said reversed image onto said first rotating electrophotographic drum in synchronization with said first drum and superposed over the electrophotographic image produced by said first projection station, a color developing station for developing the image on said first drum, an image transfer station for transferring the developed electrophotographic image from said first drum to a strip of print receiving material, and an image fixing station for permanently fixing said image to said material, third and fourth projection stations for producing together on a second electrophotographic drum a color masked image of a second color, means for developing said electrophotographic image, means for transferring said developed electrophotographic image onto said strip of print receiving material in registry with said first transferred image and an image fixing station for permanently fixing said transferred image to said material, fifth and sixth projection stations for producing together on a third electrophotographic drum a color masked image of a third color, means for developing said electrophotographic image, means for transferring the developed electrophotographic image from said third drum onto said strip of print receiving material in registry with said first and second transferred images, and an image fixing station for permanently fixing said, transferred image to said material.

7. An electrophotographic color printer for continuously producing electrophotographic color prints from original color subjects comprising three projection heads, three printing heads associated, respectively, with said three projection heads, and transport means for continuously moving a strip of color subjects through said projection stations, each of said projection heads comprising a light source for illuminating the color original and a projection lens receiving light from said color original for producing an image of said color original, a first beam splitter for dividing the light from said projection lens into a first path and a second path, a color separation filter in said first path, a color masking filter, a tone reversing image tube and an image tube projection lens in said second path, and a second beam splitter for combining the light from the two paths, each of said printing heads comprising a rotating electrophotographic drum provided with a charging station, an exposure station for receiving an image from its respective projection head, a developer station and an image transfer station for transferring said developed image to a support material.

References Cited in the file of this patent UNITED STATES PATENTS Jumeax et a1. Mar. 6, Huebner Aug. 25, Carlson Oct. 6, Huebner Sept. 24, Rackett Dec. 31, Walkup et a1 Nov. 6, Good Feb. 5, Walk-up June 3, Carlson Jan. 6, Greaves Dec. 6, Grieg Feb. 21, Jacob July 3, Crumrine et a1 Feb. 19, Paris Aug. 20, Jacob Oct. 1,

FOREIGN PATENTS France July 13,

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,986,466 May 30, 1961 Edward K. Kaprelian It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification line 4, for "(29 Riveredge Road, Red Bank, Califo)" read (29 Riveredge Road, Red Bank, N. J.)

Signed and sealed this 7th day of November 1961.

SEA L) Attest;

ERNEST W. SWIDER I DAVID L. LADD Attesting Officer I Commissioner of Patents USCOMM-DC UNITED STATES PATENT OFFICE CERTIFICATE OFCVOVRRECTIONV Patent N0. 2,986,466 May 30, i961 K Kaprelian It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification, line 4L for "(29 Riveredge Road, Red Bank, Califo)" read (29 Riveredge Road, Red Bank, N. J.)

Signed and sealed this 7th day of November 1961.

(SEAL) Attest:

ERNEST W. SWIDE R DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC 

1. A METHOD OF CONTINUOUSLY PRODUCING A STRIP OF ELECTROPHOTOGRAPHIC PRINTS IN NATURAL COLOR FROM A CONTINUOUSLY MOVING COLOR ORIGINAL THROUGH THREE-COLOR PRINTING TECHNIQUES COMPRISING THE STEPS OF PROJECTING THROUGH A COLOR SEPARATION FILTER A CONTINUOUSLY MOVING FIRST COLOR SEPARATION IMAGE, INDEPENDENTLY FORMING THROUGH A MASKING FILTER A CONTINUOUSLY MOVING FIRST COLOR MASKING IMAGE, COMBINING ON A FIRST CONTINUOUSLY MOVING ELECTROPHOTOGRAPHIC PLATE SURFACE SENSITIVE TO SAID FIRST COLOR SEPARATION IMAGE, SAID FIRST COLOR SEPARATION IMAGE AND SAID FIRST COLOR MASKING IMAGE IN REGISTRY TO PRODUCE A FIRST ELECTROSTATIC COLOR MASKED SEPARATION IMAGE DEVELOPING SAID FIRST ELECTROSTATIC COLOR MASKED SEPARATION IMAGE WITH A FIRST COLOR DEVELOPER TO PRODUCE A COLOR SEPARATION IMAGE HAVING A COLOR BEARING SUBSTRACTIVE RELATION TO SAID FIRST COLOR SEPARATION FILTER, TRANSFERRING SAID COLOR SEPARATION IMAGE TO A CONTINUOUSLY MOVING COLOR PRINT SUPPORT MATERIAL, PERMANENTLY FIXING SAID TRANSFERRED FIRST COLOR SEPARATION IMAGE TO SAID SUPPORT MATERIAL, REPEATING SAID COLOR SEPARATION AND COLOR MASKING STEPS FOR A SECOND SEPARATION COLOR THROUGH SEPARATION AND MASKING FILTERS FOR SAID SECOND COLOR TO PRODUCE A SECOND ELECTROSTATIC COLOR MASKED COLOR SEPARATION IMAGE ON A SECOND CONTINUOUSLY MOVING CHARGED ELECTROPHOTOGRAPHIC PLATE SURFACE SENSITIVE TO SAID SECOND MASKED COLOR SEPARATION IMAGE, DEVELOPING SAID SECOND ELECTROSTATIC COLOR MASKED SEPARATION IMAGE WITH A SECOND COLOR DEVELOPER TO PRODUCE A SECOND CONTINUOUSLY MOVING COLOR SEPARATION IMAGE HAVING A COLOR BEARING A SUBTRACTIVE RELATION TO SAID SECOND COLOR SEPARATION FILTER, TRANSFERRING SAID SECOND COLOR SEPARATION IMAGE ONTO SAID 